title: The Rab27a effectors JFC1/Slp1 and Munc13-4 regulate exocytosis of neutrophil granules.
abstract: Neutrophil granules contain secretory molecules that contribute to the implementation of all neutrophil functions. The molecular components that regulate the exocytosis of neutrophil granules have not been characterized. In this study, using small interfering RNA gene-targeting approaches and granulocytes from genetically modified mice, we characterized the Rab27a effectors JFC1/Slp1 and Munc13-4 as components of the exocytic machinery of granulocytes. Using total internal reflection fluorescence microscopy analysis, we show that Rab27a and JFC1 colocalize in predocked and docked vesicles in granulocytes. Next, we demonstrate that JFC1-downregulated granulocytes have impaired myeloperoxidase secretion. Using immunological interference, we confirm that JFC1 plays an important role in azurophilic granule exocytosis in human neutrophils. Interference with Rab27a but not with JFC1 impaired gelatinase B secretion in neutrophils, suggesting that a different Rab27a effector modulates this process. In similar studies, we confirmed that Munc13-4 regulates gelatinase secretion. Immunofluorescence analysis indicates that Munc13-4 localizes at secretory organelles in neutrophils. Using neutrophils from a Munc13-4-deficient mouse model (Jinx), we demonstrate that Munc13-4 plays a central role in the regulation of exocytosis of various sets of secretory organelles. However, mobilization of CD11b was not affected in Munc13-4-deficient neutrophils, indicating that secretory defects in these cells are limited to a selective group of exocytosable organelles.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Agnieszka A
authors.initials: AA
authors.lastname: Brzezinska
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Johnson
authors.forename: Daniela B
authors.initials: DB
authors.lastname: Munafo
authors.forename: Karine
authors.initials: K
authors.lastname: Crozat
authors.forename: Bruce
authors.initials: B
authors.lastname: Beutler
authors.forename: William B
authors.initials: WB
authors.lastname: Kiosses
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Ellis
authors.forename: Sergio D
authors.initials: SD
authors.lastname: Catz
mesh_terms: D001483:Base Sequence; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism*; D005089:Exocytosis; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure; D034622:RNA Interference; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins
chemical_list: D008565:Membrane Proteins; C431146:SYTL1 protein, human; C507969:UNC13D protein, human; D033921:Vesicular Transport Proteins; D000075745:rab27 GTP-Binding Proteins; D020780:Matrix Metalloproteinase 9; C066694:RAB27A protein, human; D020691:rab GTP-Binding Proteins